Heat exchanger and mounting structure of the same

ABSTRACT

A heat exchanger has tubes stacked in a direction and constructed of plate members. Each tube includes a main part for defining a passage of an internal fluid therein and a joined part that is provided by joining portions of the plate member to have surface contact. The joined part projects from an upstream end of the main part with respect to a flow of an external fluid. The joined part includes an inclined portion that is bent at a predetermined angle relative to a reference plane that is perpendicular to the direction in which the tubes are stacked.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-142509 filed on May 23, 2006, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a heat exchanger and a mounting structure of the same to a vehicle.

BACKGROUND OF THE INVENTION

In a vehicle, a heat exchanger such as a radiator and a condenser is mounted at a front space of a vehicle to receive air that is sucked from a front opening of the vehicle so as to cool an internal fluid such as a cooling water and a refrigerant. While the vehicle is traveling, if foreign materials such as stones enter the front space of the vehicle and collide with tubes of the heat exchanger, the tubes are damaged, resulting in leakage of the internal fluid.

Japanese Unexamined Patent Publication No. 2002-181463 discloses a heat exchanger that is capable of reducing such leakage of an internal fluid due to collision of foreign materials. In the heat exchanger, each tube is formed by folding a plate member so as to include a tubular-shaped main part and a joined part at which ends of the plate are joined to have surface contact. The main part defines a passage through which the internal fluid flows. The joined part extends straight from an upstream end of the main part toward an upstream position with respect to a flow of air.

With this configuration, the foreign materials will collide with the joined part of the tube, instead of the main part. When the foreign materials collide with the joined part of the tube, the joined part is crushed, and hence the energy of collision is absorbed. Accordingly, it is less likely that the main part of the tube will be damaged.

In this tube, the energy of collision is more absorbed with an increase in a dimension of the joined part toward the upstream position with respect to the flow of air. However, this results in an increase of a size of the heat exchanger. On the other hand, to increase the dimension of the joined part without increasing an entire size of the tube, a dimension of the main part is reduced. In this case, a cross-sectional area of the passage of the internal fluid is reduced. As a result, pressure loss of the internal fluid increases, and reducing efficiency of heat exchange.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter, and it is an object of the present invention to provide a heat exchanger capable of improving an effect of absorbing energy of collision of foreign materials.

According to a first aspect of the present invention, a heat exchanger has tubes stacked in a direction and constructed of plate members. Each of the tubes includes a main part for defining a passage of an internal fluid therein and a joined part at which portions of the plate member are joined to have surface contact. The joined part projects from an upstream end of the main part toward an upstream position with respect to a flow of an external fluid flowing outside of the main part. Further, the joined part includes an inclined portion that is inclined at a predetermined angle relative to a reference plane that is defined perpendicular to the direction in which the tubes are stacked.

For example, the inclined portion is formed by bending. In this case, the inclined portion retains residual stress. Therefore, if a foreign material collides with the inclined portion in a direction parallel to a bending direction of the inclined portion (e.g., arrows E in FIG. 8A), the inclined portion is easily deformed and bent in the bending direction. As such, the effect of absorbing the energy of collision is improved by the deformation of the inclined portion.

Accordingly, the energy of collision is absorbed by the inclined portion without increasing a length of the joined part toward the upstream position. The effect of absorbing the energy of collision due to the foreign material is effectively improved without increasing a size of the heat exchanger and deteriorating efficiency of heat exchange.

According to a second aspect of the present invention, a heat exchanger has tubes constructed of plate members. Each of the tubes includes a main part for defining a passage of an internal fluid therein and a joined part at which portions of the plate member are joined to have surface contact. The joined part projects from an upstream end of the main part toward an upstream position with respect to a flow of an external fluid flowing outside of the main part. Further, the joined part includes an inclined portion that is inclined at a predetermined angle relative to a reference plane that is defined parallel to a longitudinal direction of the tubes and parallel to a flow direction of the external fluid. Also in this case, the similar effects are provided.

The above heat exchanger is for example mounted in a front space of a vehicle such that the inclined portions are inclined upward, i.e., upstream ends of the inclined portions are located higher than downstream ends thereof. If a foreign material is introduced into the front space from an opening defined at a front lower position of the vehicle and collided with the inclined portion in an upward direction, the inclined portion will be easily bent upward. Thus, the energy of collision will be effectively absorbed by the bending of the inclined portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 a schematic sectional view of a heat exchanger mounted on an engine compartment of a vehicle according to a first embodiment of the present invention;

FIG. 2 is a perspective view of the heat exchanger according to the first embodiment;

FIG. 3 is a schematic perspective view of a portion of a heat exchanging part of the heat exchanger according to the first embodiment;

FIG. 4 is a schematic sectional view of a portion of the heat exchanging part according to the first embodiment;

FIG. 5 is an exploded perspective view of a tube and a tank of the heat exchanger according to the first embodiment;

FIG. 6A is a perspective view for showing an embossing step for forming the tube according to the first embodiment;

FIG. 6B is a perspective view for showing a folding step for forming the tube according to the first embodiment;

FIG. 7 is a perspective view for showing another example for forming the tube according to the first embodiment;

FIG. 8A is a schematic sectional view of a portion of the heat exchanger, before a collision of a stone, according to the first embodiment;

FIG. 8B is a schematic sectional view of the portion of the heat exchanger, after the collision of the stone, according to the first embodiment;

FIG. 9 is a schematic perspective view of a tube as a comparative example;

FIG. 10 is a sectional view of a portion of a tube of a heat exchanger according to a second embodiment of the present invention;

FIG. 11 is a sectional view of a portion of a tube of a heat exchanger according to a third embodiment of the present invention;

FIG. 12 is a sectional view of a portion of a tube of a heat exchanger according to a fourth embodiment of the present invention;

FIG. 13 is a sectional view of a portion of a tube of a heat exchanger according to a fifth embodiment of the present invention;

FIG. 14 is a sectional view of a portion of a tube of a heat exchanger according to a sixth embodiment of the present invention;

FIG. 15 is a schematic perspective view of a portion of a heat exchanger according to a seventh embodiment of the present invention; and

FIG. 16 is an exploded perspective view of a portion of the heat exchanger according to the seventh embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS First Embodiment

A first embodiment will be described with reference to FIGS. 1 to 8. In the drawings, an up and down arrow and a front and rear arrow denotes respective directions when a heat exchanger is mounted on a vehicle. Also, a right and left arrow denotes respective directions when the heat exchanger is viewed from a front of the vehicle.

Referring to FIG. 1, a heat exchanger 10 is for example used as a refrigerant condenser of a refrigerating cycle for a vehicle air conditioner. The heat exchanger 10 is mounted in a front space of a vehicle, e.g., in an engine compartment 2 of a vehicle 1, at a position where outside air is sufficiently supplied when the vehicle is running.

The vehicle has a first opening 3 and a second opening 4, at a front part of the engine compartment 2, for introducing air into the engine compartment 2. For example, the first opening 3 is located at a position corresponding to an upper portion of the heat exchanger 10, in front of the heat exchanger 10. The second opening 4 is located at a position corresponding to a lower portion of the heat exchanger 10, in front of the heat exchanger 10.

In an example shown in FIG. 1, the first opening 3 is formed between a front end of a bonnet 5 and a front bumper 6, and the second opening 4 is formed under the front bumper 6. The bonnet 5 is provided as a cover of the engine compartment 2. The front bumper 6 is located at a front-most portion of the vehicle and serves as a front shock absorbing member. Also, a front grill 7 in a form of louver is provided in the first opening 3.

The heat exchanger 10 performs heat exchange between a high temperature, high pressure refrigerant as an internal fluid, which has been discharged from a compressor (not shown) of the refrigerating cycle, and air as an external fluid, thereby condensing the refrigerant. As shown in FIG. 2, the heat exchanger 10 includes a heat exchanging part 13 and first and second tanks 14, 15.

The heat exchanging part 13 includes a plurality of flat tubes 11 defining refrigerant passages (internal fluid passages) through which the refrigerant flows and a plurality of fins 12. The fins 12 are for example corrugated fins. The first and second tanks 14, 15 are located at longitudinal ends of the tubes 11.

In this embodiment, the heat exchanging part 13 is arranged such that longitudinal direction D1 of the tubes 11 correspond to the right and left direction. Thus, the air flows through the heat exchanging part 13 from a front side to a rear side. The first and second tanks 14, 15 are provided to distribute and collect the refrigerant into and from the tubes 11. At the ends of the heat exchanging part 13, side plates 16, 17 are provided to maintain a rectangular-shaped outline of the heat exchanger 10. The side plates 16, 17 are disposed parallel to the tubes 11 and ends of the side plates 16, 17 are connected to end portions of the first and second tanks 14, 15.

For example, the tubes 11, the fins 12, and the first and second tanks 14, are integrated by brazing. The first and second tanks 14, 15 are made of an aluminum material and coated with a brazing material (filler metal). The first and second tanks 14, 15 are substantially cylindrical shaped containers. The first and second tanks 14, 15 are formed with tube insertion holes 14 a, 15 a for receiving the longitudinal ends of the tubes 11. The tube insertion holes 14 a, 15 a are arranged at predetermined intervals with respect to a longitudinal direction of the tanks 14, 15.

The first tank 14 is provided with a first connecting block 14 b. An inlet pipe is coupled to the first connecting block 14 b for introducing the high temperature, high pressure refrigerant discharged from the compressor (not shown) into the first tank 14. The first connecting block 14 b is brazed at a position adjacent to the end portion of the first tank 14, e.g., a lower portion in FIG. 2. Also, the first tank 14 is provided with an engaging projection 14 c at its end, e.g., at a lower end in FIG. 2 for fixing the heat exchanger 10 to a vehicle body.

The second tank 15 is provided with a second connecting block 15 b. An outlet pipe is coupled to the second connecting block 15 b for discharging a liquid-phase refrigerant from the heat exchanger 10 toward an expansion valve (not shown) of the refrigerating cycle. The second connecting block 15 b is brazed at a position adjacent to the end portion of the second tank 15, e.g., an upper portion in FIG. 2. Also, the second tank 15 is provided with an engaging projection 15 c at its end, e.g., at a lower end in FIG. 2 for fixing the heat exchanger 10 to the vehicle body.

Referring to FIG. 3, each of the tubes 11 is constructed of a pair of plate members (first and second plate members) 11 a, 11 b. In this embodiment, each of the plate members 11 a, 11 b is provided by a clad member that includes a thin plate made of an aluminum material and both surfaces of which are coated with a brazing material.

The first and second plate members 11 a, 11 b are joined such that the tube 11 includes a main part 18, a first joined part 19A, and a second joined part 19B. The main part 18 has a predetermined shape to define the refrigerant passages. The first and second joined parts 19A, 19B are provided at ends of the tube 11 with respect to a tube width direction D2. The first and second joined parts 19A, 19B are provided by joining portions of the first and second plate members 11 a, 11 b to have surface contact. Here, the tube width direction D2 corresponds to a direction in which a width of the tube 11 is measured and is perpendicular to the tube longitudinal direction D1.

The main part 18 is formed throughout the tube 11 in the tube longitudinal direction D1. The first joined part 19A and the second joined part 19B extend on opposite sides of the main part 18 with respect to the tube width direction D2. The first joined part 19A and the second joined part 19B extend throughout the tube 11 in the tube longitudinal direction D1.

Specifically, each of the first and second plate members 11 a, 11 b includes a base wall portion 20 and a plurality of embossed portions 21 that project from the base wall portion 20. The first and second plate members 11 a, 11 b are joined such that the base wall portions 20 make surface contact and the embossed portions 21 project in opposite directions. Further, the embossed portions 21 of the first and second plate members 11 a, 11 b are partly overlapped with each other such that refrigerant passages 23 are formed between the first and second plate members 11 a, 11 b.

The embossed portions 21 are formed at middle portions of the respective plate members 11 a, 11 b with respect to the tube width direction D2. Further, each embossed portion 21 has side walls 27 on its both sides with respect to the tube longitudinal direction D1 and a flat top wall on its end.

The side walls 27 have curved shapes and extend in the tube width direction D2 in a serpentine or meandering manner. Thus, air passage portions 30 are provided between the side walls 27 of the adjacent embossed portions 21. The air passage portions 30 extend in the tube width direction D2 in a serpentine or meandering manner.

A bottom wall of the air passage portion 30 includes a flat wall 30 c and first and second recessed portions 30 a, 30 b that are recessed from the flat wall 30 c toward an inside of the tube 11 through step portions 30 d, 30 e. For example, the first recessed portions 30 a are formed at position corresponding to peaks or most curved portions of the serpentine shape and the second recessed portions 30 b are formed at position corresponding to the end of the air passage portion 30. The first and second recessed portions 30 a, 30 b are provided by the base wall portion 20. In other word, the first and second recessed portions 30 a, 30 b are on the same level as the base wall portion 20. The flat wall 30 c is slightly embossed from the base wall portion 20 toward an outside of the tube 11.

Also, the first and second plate members 11 a, 11 b are arranged such that the air passage portions 30 are staggered in the tube longitudinal direction D1, and the first and second recessed portions 30 a, 30 b overlap. Thus, the first and second plate members 11 a, 11 b are in contact with and joined with each other at the first and second recessed portions 30 a, 30 b. In this embodiment, the step portions 30 d, 30 e have height approximately 0.65 mm, respectively.

In the tube 11, the refrigerant passage 23 has a complex serpentine shape as shown by arrows B in FIG. 3. Since the air passage portions 30 of the first and second plate members 11 a, 11 b are staggered in the tube longitudinal direction D1, the refrigerant passage 23 extends in the tube longitudinal direction D1 while meandering in a direction in which a height of the tube 11 is measured (i.e., in an up and down direction in FIG. 3).

Further, since the first and second recessed portions 30 a, 30 b of the first and second plate members 10 a, 10 b are overlapped and joined with each other, the refrigerant passage 23 diverges at the first recessed portions 30 a and merges downstream of the first recessed portions 30 a. As such, the refrigerant passage 23 extends in the tube longitudinal direction D1 while repetitively diverging and merging in the tube width direction D2. Namely, the refrigerant passage 23 is formed in a serpentine manner both in the tube longitudinal direction D1 and in the tube width direction D2.

The fins 12 are made of a bare plate without coated by the brazing material. The bare plate is for example made of an aluminum material and is formed into a corrugated shape.

Each of the fin 12 includes joining portions 12 a, 12 b to be joined with the flat top wall of the embossed portions 21 of the tubes 11 and connecting walls 12 c, 12 d extending between the joining portions 12 a, 12 b. The joining portions 12 a, 12 b are flat walls. The connecting walls 12 c, 12 d are flat walls and extend in a tube stack direction in which the tubes 11 are stacked (i.e., up and down direction in FIG. 3). Although not illustrated, the connecting walls 12 c, 12 d are formed with louvers that are formed by cutting portions of the connecting walls 12 c, 12 d and angling the cut portions so as to oppose the flow of air.

As shown in FIG. 4, the first joined part 19A, which is formed at the upstream end of the tube 11 with respect to the flow of air, includes an inclined portion 31. The inclined portion 31 is formed such that its upstream end (tip side) with respect to the flow of air is located higher than its downstream end (base side).

Specifically, the inclined portion 31 is inclined at a predetermined angle θ with respect to a reference plane S that is defined by an imaginary plane perpendicular to the tube stack direction. Also, the reference plane S is parallel to the air flow direction and the tube longitudinal direction D1.

Also, a dimension L1 of the inclined portion 31 from a first end (upstream end) 32 to a second end (downstream end) 33 is equal to or greater than 1 mm. Here, the dimension L1 is measured in a direction parallel to the reference plane S.

In the example shown in FIG. 4, the first end 32 is located at the same position as an upstream end 12 e of the fin 12 with respect to the air flow direction, i.e., the tube width direction D2. Alternatively, the first end 32 cab be located downstream of the upstream end 12 e of the fin 12 with respect to the air flow direction.

FIG. 5 shows a connecting structure of the second tank 15 and the longitudinal ends of the tubes 11. Because the connecting structure of the first tank 14 and the opposite longitudinal ends of the tube 11 is similar to the connecting structure of the second tank 15 and the longitudinal ends of the tubes 11, reference numerals regarding the first tank and the tube insertion holes of the first tank are shown in parentheses in FIG. 5. Also, in FIG. 5, the illustration of the main portions 18 of the tubes 11 is simplified.

As shown in FIG. 5, the inclined portions 31 is formed only at an intermediate portion of the first joined part 19A other than longitudinal ends. That is, the inclined portions 31 is not formed at longitudinal ends of the first joined part 19A. Therefore, the longitudinal ends of the first joined part 19A are parallel to the reference plane S. Hereafter, the longitudinal ends of the first joined part 19A are referred to as parallel portions 34. Further, the first joined part 19A includes transitional portions 35 between the inclined portion 31 and the parallel portions 34, and at which the angle θ of inclination gradually reduces toward the parallel portions 34. In other words, ends of the inclined portion 31 smoothly connect to the parallel portions 34 through the transitional portions 35.

On the other hand, the second joined part 19B, which is formed on a downstream side of the tube 11 with respect to the flow of air, extends parallel to the reference plane S. Here, the second joined part 19B has a dimension L2 that is the same as a dimension L3 of the parallel portion 34 of the first joined part 19A, with respect to the tube width direction D2.

As such, the first joined part 19A and the second joined part 19B have the symmetrical shape at the longitudinal ends of the tube 11 and asymmetrical shape at the middle portion where the inclined portion 31 is formed. It is not always necessary that the dimension L2 of the second joined part 19B is equal to the dimension L3 of the parallel portion 34 of the first joined part 19A.

Each of the tube insertion holes 14 a, 15 a defines an opening having a shape corresponding to a cross-sectional shape of the tube 11. For example, the tube insertion hole 14 a, 15 a includes a first portion 36 and second portions 37 on opposite ends of the first portion 36. The first portion 36 extends parallel to the air flow direction to corresponds to the main part 18. The second portions 37 are disposed on the ends of the first portion 36 with respect to the air flow direction to correspond to the first and second joined parts 19A, 19B. In FIG. 5, although the second portions 37 that correspond to the first joined parts 19A are illustrated, the opposite second portions 37 that correspond to the second joined parts 19B are not illustrated for reason of illustration.

As described above, the first joined part 19A and the second joined part 19B are symmetric at the longitudinal ends of the tube 11. Therefore, the second portion 37 that corresponds to the second joined part 19B have the symmetrical shape as the second portion 37 that corresponds to the first joined part 19A.

Namely, each of the tube insertion holes 14 a, 15 a is symmetric about a central point with respect to the tube width direction D2. Also, the tube insertion holes 14 a, 15 a of the first and second tanks 14, 15 have the same shape.

Next, a method of forming the tube 11 will be described. FIGS. 6A and 6B show an example of the method of forming the tube 11. As shown in FIG. 6A, the embossed portions 21 and the air passage portions including the flat walls 30 c are continuously formed on a band-shaped material sheet (work) 38, which provides the base wall 20 of the tube 11, by pressing using a pair of forming roller 39, 40 (embossing step).

In this example, the first and second plate members 11 a, 11 b are integrally produced from the one material sheet 38. Namely, the embossed portions 21 and the air passage portions 30 of the first plate member 11 a are formed on an upper half portion (first portion) 38 a of the material sheet 38 and the embossed portions 21 and the air passage portions 30 of the second plate member 11 a are formed on a lower half portion (second portion) 38 b of the material sheet 38.

The first forming roller 39 is formed with first projections 39 a and second projections 39 b. The first projections 39 a and the second projections 39 b are alternately arranged in a circumferential direction of the first forming roller 39. The first projections 39 a project from an outer circumferential wall of the first forming roller 39 for embossing the embossed portions 21. The second projections 39 b project less than the first projections 39 a for embossing the flat walls 30 c of the air passage portions 30.

On the other hand, the second forming roller 40 is formed with first recesses 40 a and second recesses 40 b for corresponding to the first projections 39 a and the second projections 30 b of the first forming roller 39. The first recesses 40 a and the second recesses 40 b are alternately arranged in a circumferential direction of the second forming roller 40.

With the rotation of the first and second forming rollers 39, 40, the embossed portions 21 and the flat walls 30 c of the air passage portions 30 are alternately and repetitively formed in a longitudinal direction of the material sheet 38. In FIG. 6A, the first projections 39 a and the first recesses 40 a are indicated by cross-hatching of solid lines and the second projections 39 b and the second recesses 40 b are indicated by cross-hatching of dashed lines, for reasons of clarity of illustration.

Next, as shown in FIG. 6B, the material sheet 38 is folded about a centerline such that ends of the material sheet 38 come into contact with each other (folding step). In this case, the ends of the material sheet 38 provides the first joined part 19A, for example. Although not illustrated, in this folding step, the ends of the material sheet 38 may be crimped to temporality or preliminarily fix the material sheet 38 to maintain this folded condition.

Then, the folded material sheet 38 is cut into predetermined length (cutting step). Thereafter, the joined ends of the material sheet 38, i.e., the first joined part 19A, are bent to form the inclined portion 31 (bending step). For example, the first joined part 19A is gradually and sequentially bent using a plurality of forming rollers (not shown), which is so-called a roll forming method. Then, the contact portions between the first and second portions 38 a, 38 b of the material sheet 38, i.e., the base wall portions 20 of the first and second plate members 11 a, 11 b are brazed (brazing step).

In this embodiment, the brazing step is performed after the tubes 11, the fins 12 and the first and second tanks 14, 15 are preliminarily fixed. Therefore, the tubes 11, the fins 12 and the first and second tanks 14, 15 are integrally brazed in this brazing step. Alternatively, this brazing step may be performed solely for the tubes 11, i.e., for brazing the fist and second plate members 11 a, 11 b. Namely, the tubes 11 may be brazed with the fins 12 and the first and second tanks 14, 15 after this brazing step.

In the above example, the bending step is performed after the folding step and the cutting step. Alternatively, the bending step may be performed before the folding step. Also, in the embossing step, the embossed portions 21 and the flat portions 30 c of the air passage portions 30 may be formed by press-forming using forming dies, instead of the roll forming using the forming rollers 39, 40.

FIG. 7 shows another example of the method of forming the tube 11. As shown in FIG. 7, the tube 11 can be formed by using two separate material sheets (works) 41, 42. Namely, the first plate member 11 a and the second plate member 11 b are separately formed by the material sheets 41, 42, respectively.

Specifically, the embossed portions 21 and the flat walls 30 c of the air passage portions 30 for the first plate member 11 a are formed on the first material sheet 41 (embossing step). Likewise, the embossed portions 21 and the flat walls 30 c of the air passage portions 30 for the second plate member 11 b are formed on the second material sheet 42 (embossing step).

Then, the first and second material sheets 41, 42 are cut into a predetermined length (cutting step). Thereafter, the first material sheet 41 and the second material sheets 42 are placed to oppose each other and make contact at predetermined portions. Next, ends of the first and second material sheets 41, 42 are partly crimped. Thus, the first and second material sheets 41, 42 are preliminarily fixed (setting step).

Thereafter, one end of the preliminarily fixed first and second material sheets 41, 42, i.e., the first joined part 19A is bent to form the inclined portion 31 (bending step). Then, the first and second material sheets 41, 42 are joined by brazing (brazing step). As such, the tube 11 is produced.

Next, an operation of the heat exchanger 10 will be briefly described. The high temperature, high pressure refrigerant, which has been discharged from the compressor (not shown), flows into the first tank 14 through the first connecting block 14 a. The refrigerant is distributed into the tubes 11 from the first tank 14.

While the refrigerant flowing in the tubes 11, heat of the refrigerant is transferred to the tubes 11 and the fins 12. The heat is further transferred to the air flowing outside of the tubes 11 in a direction generally perpendicular to the tube longitudinal direction D1. Thus, the refrigerant is condensed into the liquid-phase. The liquid-phase refrigerant is collected in the second tank 15 and discharged from the heat exchanger 10 through the second connecting block 15 a. Then, the refrigerant is introduced into the expansion valve (not shown), for example.

Next, an effect of heat exchange between the refrigerant and the air in the heat exchanging part 13 will be described. As shown by the arrows B in FIG. 3, since the refrigerant flows inside of the tubes 11 while meandering complexly, the flow of the refrigerant is disturbed. As such, the coefficient of heat transfer of the refrigerant improves. Accordingly, efficiency of heat transfer improves.

On the other hand, the air that flows through areas separated from the tubes 11 flows along the fins 12, as shown by an arrow C in FIG. 2. This air receives heat from the fins 12 and then flows out of the fins 12. Thus, the fins 12 are cooled by the air passing through the fins 12.

Also, the air that flows adjacent to the tubes 11 receives heat from the tubes 11 and is discharged from the heat exchanging part 13 after cooling the tubes 11. In this case, as the air flows through the air passage portions 30 in the serpentine manner, as shown by an arrow D, the flow of this air is disturbed. As such, the coefficient of heat transfer of the air improves. Accordingly, efficiency of heat transfer improves.

In addition, as the air is contracted when flowing into the air passage portions 30, the coefficient of heat transfer of the air improves. Further, because the surface area of heat transfer is increased by the air passage portions 30, the amount of heat radiation from the tube 11 to the air is increased.

Furthermore, the flow of air is further disturbed by the step portions 30 d, 30 e of the air passage portions 30. With this, the coefficient of heat transfer of the air further improves.

Referring to FIG. 1, while the vehicle is traveling, foreign materials such as scattered stones may enter the engine compartment 2 from the second opening 4 and collide with a front part of the heat exchanger 10, as shown by an arrow H. In this embodiment, the foreign materials may collide from a lower side toward the front part of the heat exchanger 10 due to a positional relationship between the heat exchangers 10 and the second opening 4.

Referring to FIG. 4, an angle α denotes a range of a collision angle (entry angle) in which 90% of the stones enter and collide with the heat exchanger 10. The angle α is verified as 45° below the reference plane S based on a test result.

Here, the first end 32 of the inclined portion 31 is located at the same position as the upstream ends 12 e of the fins 12 or downstream of the upstream ends 12 e of the fins 12 with respect to the flow of air. Therefore, the foreign material is more likely to collide with the fins 12 than the tubes 11. Although the fins 12 may be damaged, it is less likely that the tubes 11 will be damaged and cause leakage of the refrigerant.

In fact, it is difficult to completely avoid collision of the foreign materials with the tubes 11. In this embodiment, therefore, the following structures are employed to reduce the damages to the tubes 11 due to the collision of the foreign materials.

FIG. 8A exemplary shows a condition of the heat exchanger 10 before a stone 43 collides with the tube 11. FIG. 8B exemplary shows a condition of the heat exchanger 10 after the stone 43 collided with the tube 11 from the lower side. In this embodiment, the first joined part 19A includes the inclined portion 31 that is bent at the predetermined angle θ. As such, the inclined portion 31 retains residual stress due to the bending.

Therefore, when the stone 43 collides with the inclined portion 31 in a direction substantially parallel to a bending direction of the inclined portion 31, in which the inclined portion 31 is bent, as shown by an arrow E in FIG. 8A, the inclined portion 31 is easily bent in the bending direction. Thus, the energy of collision of the stone 43 is absorbed by this bending of the inclined portion 31. As such, it is less likely that the main part 18 of the tube 11 will be damaged. Accordingly, the leakage of the refrigerant from the tube 11 due to the collision of the foreign materials is reduced.

Further, since the inclined portion 31 is bent upward due to the collision, the stone 43 is introduced toward the upper fin 12 that is located above the tube 11 the inclined portion 31 of which has been bent. Therefore, although the fin 12 will be damaged by the stone 43, it is less likely that the stone 43 will bounce off the inclined portion 31 and collide with the main part 18. Accordingly, the damage to the main part 18 of the tube 11 is further reduced.

Also, when the inclined portion 31 is bent upward due to the collision, the plate members 11 a, 11 b are three-folded at the upstream position of the main part 18. Therefore, a thickness of the upstream portion of the main part 18 is substantially increased. Accordingly, a strength against further collision of a foreign material improves.

On the other hand, when the stone collides with the inclined portion 31 in a direction substantially parallel to the reference plane S as shown by an arrow F, the energy of collision exerted in the bending direction for bending the inclined portion 31 is smaller than the energy of collision exerted when the stone collides in the direction shown by the arrow E. Therefore, the inclined portion 31 is less likely to be bent, as compared with the case when the stone 43 is collided in the direction shown by the arrow E.

Instead, the energy of collision is exerted such that the inclined portion 31 is crushed in a direction substantially parallel to the reference plane S. Thus, the energy of collision due to the stone is absorbed by crushing of the inclined portion 31 in the direction substantially parallel to the reference plane S. Namely, the effect of absorbing the energy of collision is provided by the bending of the inclined portion 31 and the crushing of the inclined portion 31.

In a case that the stone 43 collides with the inclined portion 31 in the direction of inclination of the inclined portion 31, i.e., in a direction substantially parallel to the inclined portion 31 as shown by an arrow G, although the inclined portion 31 will not be bent, the first joined part 19A is crushed in the direction of inclination. As such, the energy of collision is absorbed.

Accordingly, the energy of collision due to the stones 43 in any directions shown by the arrows E, F G is effectively absorbed. Particularly, for the collision in the range of the angle α, the effect of absorbing the energy of collision is further improved since the inclined portion 31 is bent.

In other words, the effect of absorbing the energy of collision is improved without requiring an increase in the length of the first joined part 19A toward the upstream position with respect to the air flow direction. Namely, the effect of absorbing the energy of collision is improved without causing an increase in a size of the heat exchanger 10 and a decrease in efficiency of heat exchange.

Further, it is found that the energy of collision is sufficiently absorbed when the dimension L1 of the inclined portion 31 is equal to or greater than 1 mm. Also, the predetermined angle θ of the inclined portion 31 is equal to or less than 45°.

FIG. 9 shows a tube 11 as a comparative example. In this example, upstream ends of the plate members 11 a, 11 b are wrapped many times inside of the tube 11 to form the wrapped portions 44, 45. The wrapped portions 44, 45 are joined to each other. Thus, the first joined part 19A is provided by the wrapped portions 44, 45. In this case, the thickness of the tube 11 is increased at its upstream portion with respect to the air flow direction. Thus, the damage to the tube 11 due to the collision of foreign materials will be reduced.

However, since the upstream ends of the plate members 11 a, 11 b are wrapped many times, the productivity of the tubes 11 reduces. Also, the upstream ends of the air passage portions 30 are covered by the wrapped portions 44, 45. Therefore, the entry of the air into the air passage portions 30 are hampered by the wrapped portions 44, 45. As a result, the coefficient of heat transfer reduces, and hence the efficiency of heat exchange reduces.

In the embodiment, on the other hand, the inclined portion 31 is simply formed by bending a predetermined portion of the first joined part 19A upwardly. Thus, the productivity of the tube 11 improves. Also, the inclined portion 31 does not cover the upstream ends of the air passage portions 30. Thus, the air will smoothly enter the air passage portions 30. As such, the coefficient of heat transfer improves, and the efficiency of heat exchange improves.

In a case that the inclined portion 31 is formed throughout the first joined part 19A without forming the parallel portions 34 and the transitional portions 35, it is necessary to form the second portions 37 of the tube insertion holes 14 a, 15 a to correspond to the inclined shape of the inclined portion 31. In fact, the angle of inclination θ of the inclined portions 31 will be uneven among the tubes 11 due to the limit of forming accuracy. Therefore, when the inclined portions 31 are also formed at the longitudinal ends of the first joined parts 19A, it will be difficult to properly insert the longitudinal ends of the tubes 11 into the tube insertion holes 14 a, 15 a of the first and second tanks 14, 15.

In the embodiment, on the other hand, the inclined portions 31 are formed at portions of the first joined parts 19A other than the longitudinal ends. The first joined parts 19A have the parallel portions 34 that are parallel to the reference plane S at the longitudinal ends thereof. As such, the longitudinal ends of the tubes 11 are easily inserted into the tube insertion holes 14 a, 15 a without being affected by the forming accuracy of the inclined portions 31.

Also, the second joined parts 19B are parallel to the reference plane S. The dimension L2 of the second joined parts 19B is equal to the dimension L3 of the parallel portions 34 of the first joined part 19A. Namely, the first joined parts 19A are symmetric with the second joined parts 19B at the longitudinal ends of the tubes 11. With this, the tube insertion holes 14 a, 15 a are symmetric about the central points with respect to the air flow direction. Therefore, the tube insertion holes 14 a, 15 a are formed into the same shape. As such, equipment or facilities are shared for forming the tube insertion holes 14 a, 15 a on the first and second tanks 14, 15. Accordingly, manufacturing costs reduces.

Second Embodiment

A second embodiment will be described with reference to FIG. 10. Hereafter, structural components that are substantially the same are designated by the same reference numerals and repetitive description is omitted.

In the first embodiment, the first joined part 19A of the tube 11 is formed by overlapping and joining the ends of the plate members 11 a, 11 b. In this embodiment, the ends of the plate members 11 a, 11 b are crimped. Namely, the end of the first plate member 11 a is folded over the end of the second plate member 11 b, as shown in FIG. 10.

For example, a first end 46 of the first plate member 11 a is longer than a second end 47 of the second plate member 11 b. The first end 46 of the first plate member 11 a is folded over the second end 47 of the second plate member 11 b such that the second end 47 is wrapped by the first end 46.

Also in this case, the effects similar to the first embodiments will be provided.

Third Embodiment

A third embodiment will be described with reference to FIG. 11. In the third embodiment, the first end 46 of the first plate member 11 a and the second end 47 of the second plate member 11 b are respectively folded inwardly, and the folded ends 46, 47 are disposed to make surface contact and joined to each other. Even when the first joined part 19A is formed by the folded end 46, 47, the effects similar to the first embodiment will be provided.

Fourth Embodiment

A fourth embodiment will be described with reference to FIG. 12. In the fourth embodiment, the first end 46 of the first plate member 11 a is longer than the second end 47 of the second plate member 11 b. Only the first end 46 is folded inwardly similar to the third embodiment. The folded first end 46 is disposed to make surface contact with the second end 47 and joined to the second end 47. Even when the first joined part 19A is modified in this manner, the effects similar to the third embodiment will be provided.

Fifth Embodiment

A fifth embodiment will be described with reference to FIG. 13. In the fifth embodiment, the first end 46 of the first plate member 11 a and the second end 47 of the second plate member 11 b are folded outwardly, and base portions of the first and second ends 46, 47 are disposed to make surface contact and joined to each other. Even when the first joined part 19A is modified in this manner, the effects similar to the third embodiment will be provided.

Sixth Embodiment

A sixth embodiment will be described with reference to FIG. 14. In the sixth embodiment, the second end 47 of the second plate member 11 b is longer than the first end 46 of the first plate member 11 a. Only the second end 47 of the second plate member 11 b is folded outwardly. The first end 46 of the first plate member 11 a is disposed to make surface contact with a base portion of the second end 47 of the second plate member 11, and is joined to the base portion of the second end 47. Even when the first joined part 19A is modified in this manner, the effects similar to the fifth embodiment will be provided.

Seventh Embodiment

A seventh embodiment will be described with reference to FIGS. 15 and 16. In the first embodiment, the refrigerant passages 23 and the air passage portions 30 are provided by the base wall portions 20 and the embossed portions 21 projecting from the base walls 20 of the first and second plate members 11 a, 11 b. In the seventh embodiment, as shown in FIGS. 15 and 16, the refrigerant passage 23 is formed between the first and second plate members 11 a, 11 b, and the air passage portions 30 are formed by notched plate members 51, 52 that are provided as separate members.

In the first and second plate members 11 a, 11 b, the embossed portions 21 are formed continuously in the tube longitudinal direction D1. The first and second plate members 11 a, 11 b are opposed such that the embossed portions 21 project outside and are joined at the ends thereof to have surface contact. Thus, the tube 11 is a flat tube extending in the air flow direction. Also, the embossed portions 21 provide flat walls 53 extending along the air flow direction as planes. The refrigerant passage is defined between the flat walls 53 to extend straight in the tube longitudinal direction D1.

The notched plate member 51, 52 is interposed between the flat wall 53 of the tube 11 and the joining walls 12 a, 12 b of the fin 12, as intermediate plates. The notched plate member 51, 52 is formed with notches 54 for allowing the air to flow as the air passage portions. In this embodiment, the notched plate members 51, 52 are formed of a metallic material having high thermal conductivity.

Similar to the above embodiments, the tube 11 has the first joined part 19A and the second joined part 19B, and the first joined part 19A includes the inclined portion 31 that is bent upward. As such, the damage to the main portions 18 of the tubes 11 due to the foreign materials such as stones and the like will be reduced without requiring an increase in size of the heat exchanger 10 and causing the efficiency of heat exchange.

Also in this embodiment, the inclined portion 31 does not cover the upstream ends of the air passage portions. That is, upstream ends of the notches 54 are open in the air flow direction. Therefore, the air is smoothly introduced into the notches 54. As such, the coefficient of heat transfer improves, and the efficiency of heat exchange improves.

Other Embodiments

In the above embodiments, the heat exchanging part 13 are constructed of the stack of the flat tubes 11 and the fins 12. However, the structure of the heat exchanger 10 will not be limited to the above. For example, the heat exchanger 10 may be constructed of a plate fin type heat exchanger in which cylindrical tubes are disposed to pass through plate fins.

In this case, a main portion of the cylindrical tube is formed by two plates. A joined part of the cylindrical tube, at which the two plated are joined, is formed to project from an upstream end of the main portion toward an upstream position with respect to the air flow direction. Further, the inclined portion is formed on this joined part. Namely, a predetermined portion of the joined part is inclined with respect to a reference plane that is parallel to the longitudinal direction of the cylindrical tube.

Also in this case, the air passage portions 30 are formed on outer sides of the cylindrical tube. Thus, the coefficient of heat transfer of the air improves, similar to the above embodiments.

The shapes of the air passage portions 30 shown in the drawings are merely examples. The shapes of the air passage portions 30 may be changed in various ways. For example, the air passage portions 30 may have any shapes as disclosed in U.S. Pat. No. 6,595,273. Also, the present invention can be employed to tubes on which the air passage portions 30 are not formed.

Also, the direction of inclination of the inclined portion 31 is not limited to the upward direction. The direction may be modified in view of arrangement of the heat exchanger 10 in the engine compartment 2 and/or types of vehicles. For example, the heat exchanger 10 is placed in a condition where the foreign materials may be collided with the heat exchanger in a downward direction, the inclined portion 31 is inclined downward. Thus, the above described effects will be sufficiently provided.

It is not always necessary that all the tubes 11 have the inclined portions 31. For example, the inclined portions 31 may be formed on some of the tubes 11 that are located at a predetermined position relative to the second opening 4. That is, the inclined portion 31 may be formed on some of the tubes 11 that are more likely to be affected by the foreign materials. Also, the angle and direction of inclination of the inclined portions 31 may be varied in accordance with positions relative to the first and second openings 3, 4.

Further, it is not always necessary that the tubes 11 are constructed by the plate members 11 a, 11 b. The tubes 11 may be formed by other ways. Instead of the joined parts 19A, projections may be formed at upstream ends of the main parts 18, and the projections may be partly bent to form the inclined portions 31.

In the above embodiments, the inclined portion 31 is formed on the upstream side of the tube 11 with respect to the air flow direction. However, the inclined portion 31 may be formed on another side that is affected by collision of foreign materials depending on a condition of use or arrangement position of the heat exchanger.

In the above embodiments, the heat exchanger 10 is exemplary employed to the refrigerant condenser. However, the heat exchanger 10 is not limited to the refrigerant condenser, but may be any heat exchangers used for other purposes. Also, the internal fluid is not limited to the refrigerant.

The example embodiments of the present invention are described above. However, the present invention is not limited to the above embodiments, but may be implemented in other ways without departing from the spirit of the invention. 

1. A heat exchanger comprising: a plurality of tubes stacked in a direction and constructed of plate members, each of the plurality of tubes including a main part and a joined part at which portions of the plate member are joined to have surface contact, the main part defining a passage of an internal fluid therein for performing heat exchange with an external fluid flowing outside of the main part, wherein the joined part projects from an upstream end of the main part toward an upstream position with respect to a flow of the external fluid, and the joined part includes an inclined portion that is bent at a predetermined angle with respect to a reference plane that is defined perpendicular to the direction in which the plurality of tubes is stacked.
 2. The heat exchanger according to claim 1, wherein the predetermined angle of the inclined portion is equal to or less than 45°.
 3. The heat exchanger according to claim 1, wherein the inclined portion has an upstream end and a downstream end with respect to the flow of the external fluid, and a dimension from the upstream end to the downstream end, measured in a direction parallel to the reference plane, is equal to or greater than 1 mm.
 4. The heat exchanger according to claim 1, further comprising: a tank defining tube insertion holes in which longitudinal ends of the plurality of tubes are received, wherein the joined part extends throughout the upstream end of the main part of each tube, the joined part includes the inclined portion at a position other than a longitudinal end thereof, and the joined part includes a parallel portion at the longitudinal end thereof, the parallel portion being parallel to the reference plane.
 5. The heat exchanger according to claim 1, further comprising: a plurality of fins, wherein the plurality of fins and the plurality of tubes are alternately stacked in one of a first arrangement manner and a second arrangement manner, wherein, in the first arrangement manner, upstream ends of the plurality of fins are at the same position as upstream ends of the inclined portions with respect to the flow of the external fluid, and in the second arrangement manner, the upstream ends of the plurality of fins are located more to the upstream position with respect to the flow of the external fluid than the upstream ends of the inclined portions.
 6. The heat exchanger according to claim 1 being mounted on a vehicle such that upstream ends of the inclined portions with respect to the flow of the external fluid are located higher than downstream ends thereof.
 7. A mounting structure for mounting the heat exchanger according to claim 1 in a front space of a vehicle, wherein the vehicle defines an opening at a front lower position of the front space for allowing the front space to communicate with outside of the vehicle, the external fluid is air that is introduced in the front space through the opening, and wherein the heat exchanger is mounted such that upstream ends of the inclined portions with respect to a flow of the air are located higher than downstream ends thereof.
 8. A heat exchanger comprising: a plurality of tubes constructed of plate members, each of the plurality of tubes including a main part and a joined part at which portions of the plate member are joined to have surface contact, the main part defining a passage of an internal fluid therein for performing heat exchange with an external fluid flowing outside of the main part, wherein the joined part projects from an upstream end of the main part toward an upstream position with respect to a flow of the external fluid, and the joined part includes an inclined portion that is bent at a predetermined angle with respect to a reference plane that is defined parallel to a flow direction of the external fluid and a longitudinal direction of the plurality of tubes.
 9. The heat exchanger according to claim 8, wherein the predetermined angle of the inclined portion is equal to or less than 45°.
 10. The heat exchanger according to claim 8, wherein the inclined portion has an upstream end and a downstream end with respect to the flow of the external fluid, and a dimension from the upstream end to the downstream end, measured in a direction parallel to the reference plane, is equal to or greater than 1 mm.
 11. The heat exchanger according to claim 8, further comprising: a tank defining tube insertion holes in which longitudinal ends of the plurality of tubes are received, wherein the joined part extends throughout the upstream end of the main part of each tube, the joined part includes the inclined portion at a position other than a longitudinal end thereof, and the joined part includes a parallel portion at the longitudinal end thereof, the parallel portion being parallel to the reference plane.
 12. The heat exchanger according to claim 8, further comprising: a plurality of fins, wherein the plurality of fins and the plurality of tubes are alternately stacked in one of a first arrangement manner and a second arrangement manner, wherein, in the first arrangement manner, upstream ends of the plurality of fins are at the same position as upstream ends of the inclined portions with respect to the flow of the external fluid, and in the second arrangement manner, the upstream ends of the plurality of fins are located more to the upstream position with respect to the flow of the external fluid than the upstream ends of the inclined portions.
 13. The heat exchanger according to claim 8 being mounted on a vehicle such that upstream ends of the inclined portions with respect to the flow of the external fluid are located higher than downstream ends thereof.
 14. A mounting structure for mounting the heat exchanger according to claim 8 in a front space of a vehicle, wherein the vehicle defines an opening at a front lower position of the front space for allowing the front space to communicate with outside of the vehicle, the external fluid is air that is introduced in the front space through the opening, and wherein the heat exchanger is mounted such that upstream ends of the inclined portions with respect to a flow of the air are located higher than downstream ends thereof.
 15. A heat exchanger comprising: a plurality of tubes, each of the tubes including a main part defining a passage through which an internal fluid flows for performing heat exchange with an external fluid flowing outside of the main part, wherein the main part includes a first main wall and a second main wall opposed to each other such that the passage is defined therebetween and the external fluid flows along outer surfaces of the first and second main walls, each tube further includes a projection projecting from an outer peripheral end of the main part, and the projection is bent at a predetermined angle relative to a reference plane that is parallel to the first and second main walls. 